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Peak sun hour: concept and calculation
In this post, we’ll explain what Peak Sun Hour (PSH) is, why it’s so important, which factors can affect it, and how you can calculate it based on your location. At Endesa, we believe that understanding your energy is the first step toward making the most of it.
Solar energy isn't just about installing panels and waiting for the sun to do its job... To get the most out of a photovoltaic system, it’s essential to understand basic concepts like peak sun hour. This metric is a key factor in estimating how much usable solar energy a specific area receives daily —and it’s vital for accurately sizing any self-consumption system.
What is a peak sun hour?
PSH represents the number of hours per day during which solar radiation reaches an intensity of 1,000 W/m² —the standard value used to measure solar energy production. It doesn’t mean the sun shines at that exact intensity for several hours in a row. Instead, it’s calculated as an equivalence. For instance, if an area receives 5,000 Wh/m² in a single day, it is considered to have had 5 peak sun hours.
This data helps estimate how much energy a photovoltaic installation can generate depending on its capacity and location. The more peak sun hours an area has, the greater its energy production potential.
Why PSH matters for your solar panel performance
Knowing your area’s PSH is crucial for several reasons:
- Correctly sizing your solar system: Understanding how many panels you need to meet your consumption.
- Estimating production: Predicting how much energy you’ll generate daily, monthly, or annually.
- Optimising self-consumption: Knowing your peak sun hours helps you plan your habits around the hours of highest solar radiation.
- Assessing your investment’s profitability: You can estimate how much you’ll save on your electricity bill.
In short, PSH transforms solar radiation into useful data that helps you make smart energy decisions.
Factors that influence peak sun hour
PSH is not a fixed value. In fact, it varies depending on multiple factors that affect the amount of solar radiation reaching the Earth’s surface.
Geographic latitude
The closer you are to the equator, the more solar radiation you receive throughout the year. That’s why provinces in southern Spain usually have more peak sun hours than those in the north. To measure this parameter, it’s important to consider the Earth’s tilt and the sun’s trajectory, since they directly influence the result.
Climate
Weather conditions also play a key role. Areas with more cloudy, rainy, or foggy days receive less usable radiation. Meanwhile, regions with clearer skies and lower humidity tend to have higher PSH. Still, it’s worth noting that dust and pollution can also reduce solar intensity.
How can we calculate peak sun hour?
There are several ways to estimate an area’s PSH. Some examples include:
- Meteorological databases: Organisations like IDAE or PVGIS provide maps and tables with average values by province.
- Solar simulators: Some online tools allow you to enter your location and get personalised data.
- Technical studies: Specialised companies perform detailed analyses for specific installations.
There’s also a basic formula for calculating daily solar production: To get the value, multiply the installed capacity (kW) by the total peak sun hours. You must also account for the system's efficiency.
Daily Production (kWh) = Installed Capacity (kW) × PSH (hours) × System efficiency
For example, if you have a 3-kW system in an area with 5 peak sun hours and an efficiency of 80% (the standard for a well-installed, well-maintained system), you would generate 12 kWh/day.
3 kW × 5 PSH × 0.8 efficiency = 12 kWh/day
This calculation helps you both set realistic expectations for your photovoltaic system and plan your consumption more precisely.
PSH by province
Spain is one of the countries with the highest solar radiation across most of its territory. However, there are still significant differences between regions. Here is an approximate reference of average annual PSH by province:
| Province | Avg. PSH (hours/day) |
|---|---|
| Almería | 5.5 – 6.0 |
| Murcia | 5.5 – 6.0 |
| Seville | 5.4 – 5.9 |
| Málaga | 5.3 – 5.8 |
| Valencia | 5.2 – 5.7 |
| Zaragoza | 5.0 – 5.5 |
| Madrid | 4.8 – 5.3 |
| Barcelona | 4.6 – 5.1 |
| Bilbao | 3.8 – 4.3 |
| A Coruña | 3.5 – 4.0 |
Remember that these values are indicative and may vary depending on the month, altitude, and local conditions.
How to make the most of PSH
At Endesa, we help you maximise the benefits of your solar installation. Whether through physical panels or solutions like Tu Casa Solar Virtual, you can enjoy solar energy without worrying about the installation. Furthermore, our advisory services allow you to track your consumption and manage your surplus while choosing the most efficient electricity plan for your home.
Peak sun hour is just the beginning. The key is using that data to make decisions that help you save, consume more efficiently, and protect the planet.
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